"That bunch of characters, that group of actors playing them, that much money? Kind of a no-brainer!" Whedon laughed.

"The Avengers" is the culmination of years of planning, dating back to the first after-credit appearance of Nick Fury (Samuel Jackson) in 2008's "Iron Man." Whedon knew that balancing the huge ensemble cast would be the film's biggest challenge, and that all-star interplay would either make or break the movie.

"It had to be earned from moment to moment, and that was exhausting. [It] was still going on in the editing room after we shot it," Whedon said. "It's the same problem I had with 'Serenity' and swore I'd never have again -- tracking the information is more difficult because its not as much fun as tracking the emotion of the thing."

As with much of Whedon's prior television and film work, from "Firefly" and "Serenity" all the way back to "Buffy The Vampire Slayer," "The Avengers" involved writing and directing a huge cast. It was due to this, the writer/director stated, that most of his time was spent structuring the film.

"Organizing is and was the most exhausting part of the film. The stuff between the characters, that's just booze and candy," Whedon said with a chuckle.

The writer/director laughed again when asked about his recent foray onto the social link aggregator Reddit where Whedon did an AMA, an Ask Me Anything, where Internet fans excitedly posted questions about his past work.

"I'm a little confused by the whole Reddit thing...It seemed to be a Q&A, I enjoy those, but I don't know why it's an exciting one. Tell me, why was it cool?" Whedon asked as the actors and reporters laughed.

"The highlight was any question that wasn't about why I kill characters. Any question where they don't ask me that is a good day," Whedon added with a grin.

Getting back to "Avengers," Whedon stated his belief that the very best comic book movie adaptations capture the essence of the comics rather than copying them to the letter or ignoring them completely. "I think you see things like 'League of Extraordinary Gentlemen' where they throw out the comic, or 'Watchmen' where they do it frame for frame, and neither of them work. You have to have the spirit of the thing and then step away from that," Whedon said, "I think 'Spider-Man,' the first one particularly, figured out the formula."

Clark Gregg, who plays the popular S.H.I.E.L.D. Agent Coulson, praised Whedon both for his handling of the cast and for beefing up his own role in the film, making his character an integral part of "The Avengers."

"I just didn't think it was feasible to have this many characters and have them all move forward and having them come together...and if it did happen, I found it unlikely that Agent Coulson would do anything but blink and bring coffee to somebody," Gregg said, expressing his initial doubts about Marvel's long-running plans for the film. "When I read [the script] and saw that it was my fanboy wet dream of an 'Avengers' script and that Coulson was part of it, that was the great day for me."

"I liked...when I got to see everyone sitting at the table for the first time and I got to stand back and see everybody," added Colbie Smulders, the "How I Met Your Mother" actress who plays Nick Fury's second in command, Agent Maria Hill.

Jeremy Renner's archery training and research had to go out the window when it came time to shoot his stunts

"To see everyone finally assembled, it was an extraordinary moment and just the picture of the Avengers. It was amazing," said Hiddleston, who reprised his role as Loki as the "Avenger's" main villain. A British-born actor, Hiddleston explained that as a kid he grew up reading comics like "Beano" and "The Dandy" rather than DC and Marvel's superhero epics.

"I was introduced to American comics through the movies. Christopher Reeve's Superman was the first superhero I ever conceived of when I saw the movie when I was six," Hiddleston said.

Talking specifically about his take on Loki, Hiddleston called Thor's half-brother "such a great character. Never mind the iconography -- it's like playing an iconic Shakespeare character, it's just a privilege to be asked. A character like Loki has such a level of complexity and so many layers to him, so many things to explore, especially when he's written the way he was by Joss...the film was called 'The Avengers,' but Loki was almost on every page.

"He had taken what I did with Kenneth Branagh and he took it further. He was as damaged and psychologically interesting as I hoped it would be," Hiddleston said.

In fact, there was only one part of playing the Asgardian baddie that Hiddleston could have done without: the two-hour process to get on his Loki costume.

Though Jeremey Renner, who plays master assassin and sharpshooter Hawkeye, did not have such costume woes, he admitted he had a hard time trying to reconcile the archery training and research he did for the role with his actual stunts.

"I realized very quickly that I couldn't really use it in the film. It ended up being superhero archery...shooting behind my back, my shoulder," Renner said.

Laughing, he added, "[Black Widow actress] Scarlett [Johansson] and I beat each other up pretty good. It's fun! I like being beat up by Scarlett, wouldn't you?"

While Marvel is the first major comic book movie to boast this type of ensemble cast, there has been talk of DC Entertainment creating a "Justice League" movie, incorporating their biggest superheroes in an ensemble, a fact that has not been lost on Whedon.

"It's enormously difficult to take very disparate characters and make them work, and DC has a harder time of it than Marvel because their characters are from a bygone era where characters were bigger than we were," Whedon said. "They've amended that, but Marvel really cracked the code in terms of, 'Oh, they're just like us!' So a dose of that veracity that Marvel started with 'Iron Man', I think you need to use that as your base."

Whedon and Mark Ruffalo discuss a scene from "The Avengers"

In fact, fans have taken to the big screen versions of Marvel's heroes so well, Whedon finds himself surprised at the level of debate over which alien race should be used as Loki's movie minions.

"They are not one of the key races and they don't have a big history, and that wasn't the point," Whedon said. Laughing, he continued, "I know this debate will go on long after I'm dead, so I'll say it was the Kree/Skrull race and make everyone angry!"

The director also confessed he purposely ditched most of the supporting casts from the other Marvel films when writing "The Avengers."

"My instinct was to not have anybody from any of them, partially because you need to separate the characters from their support systems in order to create the isolation you need for a team, but also [so] when they went back to their own movies, they'd have something 'The Avengers' didn't have," Whedon explained.

The exception to the rule is Gwyneth Paltrow's appearance as Pepper Potts, Tony Stark's right hand woman and love interest. "That was really Robert's thing. He pushed hard, he didn't want to be 'crazy alone guy' -- he wanted to be 'crazy in a relationship guy,' and he really thought Gwyneth would bring something great to the table," Whedon said. "[Tony Stark's] been through two movies, he's had more a journey and he's in a more stable place, but he can still be that and be completely isolated form the world in his giant tower that he built and owns."

Paltrow was not the only cameo Whedon was excited for, as the film also features a scene where Bruce Banner, played by Mark Ruffalo, de-Hulks in front of none other than character actor Harry Dean Stanton.

"I needed to get Banner from the horror of what he'd done [in the 'Hulk' film]...to a place where he'd be prepared to go back into that state. It thought a lot about it and realized he needed someone who would just accept him," said Whedon, adding that there was no one more accepting than Stanton. Writing a scene where Banner talks to an old man who is unfazed by his Hulking, "It was not little, it was 12 pages long. I thought, 'Oh, this is great, Bruce Banner falls into a Coen Brothers movie!' The fact that they even let me keep that concept and we got Harry Dean Stanton was amazing."

Ultimately, Whedon emphasized the ensemble nature of the movie, the director/writer points to the relationship between Tony Stark and Steve Rogers as one of the major emotional tent poles of the film.

"'Captain America' was kind of my ground zero for the film," Whedon said. "The idea of someone who had been in World War Two and seen people laying down their lives in the worst circumstances in a world where the idea of community and the idea of a man meant being somebody who is part of something, as opposed to being apart from something or more famous than something or bigger than it -- it's a very different concept of manhood. The way it's kind of devolved from Steve to Tony is kind of fascinating.

"The idea of a soldier is very different than the idea of the superhero," Whedon continued. "I wanted to from the start make a war movie, I wanted to put these guys through more than what you go through in a normal superhero movie."